Long ago, when early sailors set out on their journeys across the open sea, they had to constantly know where their ship was. This meant figuring out the exact point where the ship's longitude and latitude met. To determine latitude, navigators used special tools to measure the angle between the horizon and the sun at noon or between the horizon and a fixed star.
At first, sailors relied on the astrolabe to measure the sun’s height above the horizon. However, because the deck of a ship moved up and down with the waves, using the astrolabe was very challenging and often inaccurate. As a result, people began using a different instrument—a right-angled device that made it easier to measure angles.
Over time, more advanced tools were developed, such as the two-foot gauge, protractor, and parallel ruler, which helped in navigation. In 1731, John Hadley invented the Reflective Quadrant, a clever device that could measure 1/6 of a circle. He later improved this by creating the sextant, an instrument that became crucial for maritime navigation.
The sextant allowed the observer to see both the horizon and the sun through mirrors, making it possible to measure the angle between them accurately. The scale on the quadrant provided precise readings, and the British Admiralty tested a 90-degree version on a speedboat in 1732. The results were so accurate that the quadrant quickly became a standard tool for naval navigation.
In 1757, Captain Campbell further refined the design by increasing the arc to 120 degrees, turning it into a true sextant. This new version had a triangular frame, a curved plate, a top scale, and a movable pointer. The mirrors reflected the two objects being measured, allowing sailors to calculate their latitude easily and stay on course during long voyages.
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